Very often, for optical and/or aesthetic reasons, the mask of a motor vehicle headlamp must be metallized. This mask may cover not only the dipped beam lights, the full beam lights and the sidelights, but also the direction indicator. A transparent screen that is amber in color must then be placed in front of the direction indicator.
One solution consists in using a part that is made of an amber-colored plastics material and is suited to the mask; this part is fixed to the mask.
However, the addition of this additional part entails a significant additional cost which is due not only to the cost of the part itself but also to the assembly of the mask and the part.
The metallization of the mask also causes the reflection of light in certain zones, thus causing parasitic light rays. It is also possible to find zones of parasitic reflection at the reflector of the headlamp, which is itself metallized so as to exert its optical function of reflection.
One solution consists in making matt the zones that cause parasitic light rays, by texturing (ridges) the mould that is used to produce the mask.
The implementation of such a solution nevertheless causes some problems.
This is because the use of a mould with particular texturing makes the use of this mould relatively inflexible for other applications.
Moreover, the mould may easily wear out or be contaminated by impurities.
Furthermore, the zones of parasitic reflection are not located at the same point of the reflector, depending on whether the latter is used for a vehicle with right-hand or left-hand drive. Two different moulds are thus necessary for producing these two types of reflector.
Finally, in the case of a reflector, the material used is a thermosetting material, an injected metal or stamped sheet metal, since the reflector is used for full beam lights which heat up to high temperatures, thereby making it impossible to use a thermoplastics material; for this type of thermosetting material, the texturing of the mould is impossible since it causes problems of crumbling at the time of removal from the mould.